Napa Valley
Mountain and valley, and the fog line between them.
Napa is a funnel. Cool air and fog come up from San Pablo Bay at the south end and the valley warms steadily as you go north: in 2023 Carneros logged about 3,088 growing degree-days and Calistoga about 3,687, nearly 600 more. That is why the south grows Chardonnay and Pinot Noir and the north grows Cabernet that ripens easily.
Across the valley it is mountain against floor. The floor is deep gravel and clay washed down from the hills, with hot afternoons and nights cooled by the bay air, so its day-to-night swing is wide, 40°F and more at Calistoga. The mountains rise above the fog line (Howell Mountain's boundary is drawn at 1,400 feet): cooler days, warmer nights, thin volcanic and sedimentary soils, smaller berries and firmer tannin. The west side loses the late-afternoon sun to the Mayacamas; the east side keeps it.
Switch between fog, day and night, and sun. Our vineyards are on the map and on the chart beside it; tap any two to compare them and see the slice of land between them.
Curve shapes are illustrative; the size of each swing is from published figures.
Every producer on this plate
Pick a producer to light up their vineyards and see where each wine comes from.
How the fog is drawn: the marine layer is modelled as a flat-topped sheet of cold air coming in from open water. It fills every low place it can reach without climbing over higher ground, out to a distance that follows the usual summer day. Real days vary, and the model ignores wind and warmth, so treat it as a picture of the pattern rather than a forecast.
Heights marked as the grower's figure come from our producer notes; others are read off the elevation data at the pin. Soil notes come from the producers' technical sheets.
Sources: elevation from AWS Terrain Tiles (USGS and other public data); AVA boundaries from the UC Davis Library AVA Digitizing Project.
On to Langhe & Roero · back to the United States.